Tea Time Numerical Analysis · Problem 1.2.14

Preliminaries — Leon Brin

Mathematics — Numerical Analysis · taylor-polynomial-error

Problem

Find the second Taylor polynomial, P2(x)P_2(x), for f(x)=excos⁡xf(x) = e^x \cos x about x0=0x_0 = 0. ((a)) Use P2(0.5)P_2(0.5) to approximate f(0.5)f(0.5). Find an upper bound on the error ∣f(0.5)−P2(0.5)∣|f(0.5) - P_2(0.5)| using the remainder term and compare it to the actual error. ((b)) Find a bound on the error ∣f(x)−P2(x)∣|f(x) - P_2(x)| good on the interval [0,1][0, 1]. ((c)) Approximate ∫01f(x) dx\int_0^1 f(x)\,dx by calculating ∫01P2(x) dx\int_0^1 P_2(x)\,dx instead. ((d)) Find an upper bound for the error in (c) using ∫01∣R2(x)∣ dx\int_0^1 |R_2(x)|\,dx and compare the bound to the actual error.

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